The present invention relates to a composite substrate made from silicon and ceramic.
The integration of semiconductor chips on ceramic carrier substrates, which may incorporate a wiring structure and passive electronic components and which serves as tan electrical connection of a complete system, is an established method. The bond between the completed semi-conductor chip and the ceramic carrier is usually achieved by means of bonding methods such as flip-chip bonds, different soldering techniques or adhesion methods with subsequent wire-bonding for the creation of the electrical connection.
These connection techniques generally require additional auxiliary means such as metallization, soldering, or special adhesives, and usually require a high calibration and installation efforts.
It is also known how to manufacture multi-layer circuits using sintered ceramic carriers with low-temperature co-fired ceramics (LTCC). In this way conduction paths, resistors, coils or also fluid channels can be produced. The elements can be applied by means of screen printing or photochemical processes. The unprocessed or green ceramic foils are individually structured, stacked thereafter, and laminated. Finally a defined sintering profile is executed with a peak temperature of about 850-900° C.
A more recent method has been experimentally introduced in [C. Rusu et. al, LTCC interconnects in microsystems, Journal of Micromechanics and Microengineering, 16 (2006), page 13-18].
It initially describes the possibility of connecting an LTCC ceramic with silicon by means of anodic bonding. Among other things, the connection of a 2×2 cm2 sized ceramic substrate with a silicon wafer by means of anodic bonding is shown. In this context a special low temperature ceramic (Low Temperature Cofired Ceramics—LTCC) is utilized which permits the anodic bonding of the ceramic on silicon because of its consistency and an average to low thermal expansion coefficient. Nonetheless the initially fired low-temperature ceramic must be prepared for the bonding process through additional, elaborate process steps, such as grinding and polishing. Furthermore an additional device is required for anodic bonding. Even small imperfections in the surface or deposited particles lead to gas enclosures that negatively affect the durability of the connection.
A simple silicon-ceramic bond can be produced by means of laminating and sintering of the bond partners [M. Fischer et. al, Bonding of ceramic and silicon—new options and applications, Smart Systems Integration, 2007] by initially laminating the unprocessed or green ceramic onto the nano-structured silicon surface. A sintering process is subsequently performed. As a result elaborate polishing of the ceramic is omitted.
It is the purpose of the present invention to provide a silicon-ceramic composite substrate of high mechanical strength and variable functionality that can be manufactured economically and free of auxiliary materials and which can be further processed using known, standard semiconductor process technology.